Punching apparatus

ABSTRACT

A punching apparatus, preferably for punching intermittently moving webs of synthetic thermoplastics, comprises top and bottom tools, which are mounted in a machine frame and at least one of which is connected to a drive for moving said one tool up and down. The tools for making the punching cut consist of a knife plate or a knife ring and a backing plate or a backing ring and at the end of the punching cut strike against each other or almost contact each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a punching apparatus, preferably for punchingintermittently moving webs made of synthetic thermoplastics, whichapparatus comprises top and bottom tools, which are mounted in a machineframe and at least one of which is connected to a drive for moving saidone tool up and down.

2. Description of the Prior Art

Punching apparatuses of various kinds are known in differentembodiments. But they usually cut like shears so that the cooperatingcutting edges of the top and bottom tools do not strike against eachother but move one beside the other with a clearance so that thepunching cut is effected into an unsupported portion of the materialbeing punched.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a punching apparatus whichis of the kind described first hereinbefore and which is capable ofmaking neat cuts.

In accordance with the invention that object is accomplished is apunching apparatus of the kind described first hereinbefore in that thetools for making the punching cut consist of a knife late or a knifering and a backing plate or a backing ring and at the end of thepunching cut strike against each other or almost contact each other. Thepunching apparatus in accordance with the invention comprises punchingtools having hard surfaces striking against each other and the use ofsuch apparatus will be particularly desirable and suitable when webs ofthermoplastic material are to be punched, e.g., in the manufacture ofbags or sacks.

In accordance with a further feature of the invention a carrier memberof the movable tool assembly is provided with a guide for a connectingmember used to move said movable die, and a hard-elastic and/orhard-plastic pad is provided for holding said connecting member againsta stop, which when viewed in the direction in which it is driven isdisposed at the rear end of the guide. During a punching cut in whichhard parts strike against each other said pad ensures not only therequired yieldability but will also act as a shock absorber so that thevibrational load on the apparatus will be decreased.

In numerous applications two punching apparatuses must be mounted onebeside the other in the machine frame so that said two apparatuses willmutually independently perform punching cuts in a web, which ispreferably intermittently conveyed. But two punching apparatuses whichmake punching cuts independently of each other will give rise tovibrations in the machine frame and said vibrations will adverselyaffect the respective other punching apparatus or other processingapparatus, such as welding means.

For this reason it is a further object of the invention to provide meansfor supporting and movably mounting two or more punching apparatuses ina machine frame in such a manner that they will not be adverselyaffected in operation by shock stresses produced by them. This meansthat mounting means are to be provided by which a plurality of mutuallyindependently acting punching apparatuses are mounted in such a mannerthat shocks or vibrations will be decreased or damped by each mountingmeans.

This object is accomplished in a manner for which independent protectionis claimed and which resides in that two punching apparatuses areprovided in the machine frame, the top tools and the bottom tools,respectively, of said punching apparatuses are associated with eachother and are respectively secured to two parallel frame plates, whichare separate from each other, or to side bars carrying said frameplates, those of said frame plates which carry top tools and bottomtools, which are respectively associated with each other, arerespectively interconnected by upper crossbeams, and all frame platesare fixedly interconnected at their lower ends. In that mountingarrangement in accordance with the invention the tools of each punchingapparatus are movably mounted or supported on frame plates or on sidebars which carry frame plates and said frame plates and/or side barsconstitute independent sub-frames, which at their top ends areinterconnected by beams and are jointly connected only at their bottomends. Because the machine frame is thus composed of pairs of frameplates, which constitute parts of sub-frames, the shock and vibrationalstresses are considerably reduced in a surprising manner. This may bedue to the fact that the vibrations offset each other at the jointfixing means provided at the bottom, or this may be due to differentreasons, which still have to be investigated. The frame plates of agiven sub-frame may contact each other or may be spaced apart.

In a preferred arrangement, each pair of juxtaposed frame platesconstitute an outer frame plate and an opposite inner frame plate, whichconstitute carrying plates for associated top and bottom tools. Owing tothat staggered arrangement the distance between the frame plates forcarrying a given punching apparatus will always be the same.

In accordance with a further feature of the invention, three or morepunching apparatuses are provided, two parallel groups of frame platesare associated with each punching apparatus and the outer frame plate ofone group and the inner frame plate of the other group and thesucceeding ones constitute the sub-frames for mounting a punchingapparatus.

The associated frame plates or side bars are suitably provided on theirtop and bottom sides with raised portions, which are consecutivelyarranged in the longitudinal direction, and the top and bottom tools arelongitudinally slidably guided on and adapted to the fixed to the raisedportions. Each sub-frame suitably comprises two parallel side bars forholding and guiding top and bottom tools, which are respectivelyassociated with each other.

The top and bottom tools may be mounted on carriages which are slidableon and adapted to be fixed to the frame plates or the associated sidebars.

The upper carriages may comprise laterally protruding arms, which bymeans of sliders and/or rollers are supported on the sliding surfaceswhich are constituted by the raised portions. The lower carriages may besupported by upper rollers or sliders carried only by upper arms andriding on the tracks which are constituted by the elevated portions inan arrangement in which the carriage is urged against the rails by aresilient cantilever arm, and a screw is provided for a longitudinaladjustment of the lower carriage. The resilient retaining arm may besecured to a lower crossbeam, by which the groups of left-hand andright-hand sub-frames or frame plates are interconnected. The adjustingscrew can be used to effect a fine adjustment of the punching toolsduring operation if the punching cut is inaccurate.

The movable punching tool is usually moved up and down by a pneumaticpiston-cylinder unit. But such piston-cylinder unit inherently cannot beused to provide a desired motion characteristic. For this reason it is afurther object of the invention to provide a punching tool drive whichwill impart a desired motion to the moving punching tool.

That object is accomplished in accordance with the invention in thatpreferably the upper tool assembly is carried by a guide member that isaxially slidably and non-rotatably guided in a slide bushing of a holderand is provided with a peripheral groove, which has side faces thatconstitute tracks for slide cams or slide rollers, which are secured toaxles of a pressure-applying head, which is mounted in the frame to berotatable about the axis of the guide member and is axially fixed andwhich ia connected to drive means for imparting a continuous rotation ora reciprocating motion to said head, and the tracks are so shaped thatthe pressure-applying head by its rotation or pivotal movement willimpart the desired up end down motion to the guide member.

In that case the tracks may be so designed that the guide member will beoperated with a motion characteristic which is optimally adapted to thedesired cutting operation.

The pressure-applying head is desirably rotatably mounted on a pin,which is secured to a yokelike carrier of frame or the carriage and isformed with a central bore, in which a pinlike top extension of theguide member is axially slidably guided.

In accordance with a further feature of the invention, associated axlesof the pressure-applying head include an angle of 90 degrees, with eachother, cam follower rollers are coaxially mounted on mutually oppositeaxles, two of said cam follower rollers ride only on the lower track andtwo only on the upper track of the track groove, the lower side face isprovided with mutually opposite raised portions, the upper side face isprovided with mutually opposite, complementary recesses, and said raisedportions and recesses are spaced 90 degrees apart. The raised portionsand recesses can be so designed that the desired drive motion will beimparted to the guide member. That drive motion is preferably performedin such a manner that a higher acceleration is imparted at the beginningof the movement and the movement is performed only at a lower velocitytoward its end so that the punching tools will strike against each otherat a reduced velocity. Each roller bears on the upper or lower side faceof the peripheral groove in such a manner that the rollers hold andguide the guide member substantially without a backlash in the axialdirection.

The guide member is suitably provided around its periphery with axiallyextending multiple splines, which are guided in corresponding grooves ofthe guide bushing of the carriage.

The design cf the punching apparatus in accordance with the inventioncan similarly be adopted for twin presses, which differ from twinpunching apparatuses merely in that cooperating press tools are providedrather than cooperating punching tools. For this reason, protection isalso claimed for similarly designed twin presses, in which the punchingtools have been replaced by compression molds consisting each of a punchand die.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation showing a twin press, partly in section.

FIG. 2 is a sectional view taken on line II--II in FIG. 1 and showingthe twin press.

FIG. 3 is a sectional view taken on line III--III in FIG. 1 and showingthe twin press.

FIG. 4 is a longitudinal sectional view showing the development of thecam portion for controlling the stroke of the press.

FIG. 5 shows the frame which carries the press in a perspective view, inwhich the frame parts are exploded for clearer representation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An illustrative embodiment of the invention will now be explained morein detail with reference to the drawing.

The apparatus which will be explained will be described hereinafter as atwin press even though the apparatus is used to make punching cuts. Theterm "twin press" has been adopted because the punches 29 and the dies50 may consist of punching tools or of compression molds.

In FIG. 1 the two top parts of the twin press are designated 1 and 1'and the two base parts of the press are designated 2 and 2'. The frameswhich carry said parts are apparent from FIG. 5 and are designated 3, 4,5 and 6. It is apparent from FIGS. 2 and 3 that the frames 3 and 4contact each other and so do the inner and outer frames 5 and 6. Theframe parts 3 and 4, on the one hand, and 5 and 6, on the other hand,are shown spaced apart in FIG. 5 only for sake of a clear showing. Theframes are fixedly interconnected in their bottom portion by bars 7 and8, which are rectangular in cross-section. The top portions of theframes 3 and 5 are fixedly interconnected by bars 9 and 10. The topportions of the frames 4 and 6 are fixedly interconnected by bars 11 and12. It is also apparent from FIG. 5 that the frames 3 and 5 areidentical and so are the frames 4 and 6.

it is apparent from FIG. 2 that the base part 2 rests on the two frames3 and 5 and, as is apparent from FIG. 3, the base part 2' rests on theframes 4 and 6. As a result, any loads which are applied to the basepart 2 and resulting slight resilient defection of the two frame parts 3and 5 cannot be transmitted to the base part 2' because the latter, ashas been mentioned, rests on the frames 4, 6 rather than on the frames3, 5. The top part 1 which is associated with the base part 2 consistsof a frame 13, which by means of the cantilever arms 15 of the holder 14and by clamping members 16 connected to the frame 13 is clamped to thetop portions of the two frames 3 and 5. When the clamped joints havebeen loosened or released, the top part 1 can be displaced like acarriage on the associated side bars of the frame. The identical othertop part 1' is analogously clamped to the upper portions of the twoframes 4 and 6 by the cantilever arms 15' and the two clamping members16'.

The holder 14 contains a guide member 17, which is slidably guided inthe holder 14 by means of a key 18. A connecting member 19 is screwedfrom below into the guide member 17 and carries a depending extension20, which is disposed behind a cover 21, which defines a cylindricalspace 22 in a carrier 23. A hard rubber buffer 24 rests on the bottom ofthe cylindrical space 22 and at that end which faces away from thebottom of the cylindrical space bears on the extension 20.

Pins 25 are fixed to the carrier 23 and extend with a small clearancethrough an upper arm 26 of a tool-holder that is generally designated27. The pressure-applying plate 28, which carries the punch 29, isprovided at the bottom end of the pins 25.

The guide member 17 is fixed to a cover 30, which is provided with aninternal cam track 31. Another cover 32 is provided, which is spacedfrom the cover 30 and is also provided with an internal cam track 33.The two covers 30 and 32 are fixed to each other by a member 34, whichhas been turned on a lathe. The control assembly which is constituted bythe two covers 30 and 32 and the lathe-turned member 34 is provided withan upstanding pin 35, which is movably mounted in a bore 36 of aretaining pin 37, which is fixedly secured by a screw 37' into the frame13.

A pressure-applying head 38 is rotatably mounted on the retaining pin37. A gear segment 39 is screw-connected to the head 38 and meshes witha pinion 40 of a gearmotor 41 so that the latter is operable to rotatethe pressure-applying head. The pressure-applying head 38 has at itsbottom a recess 42, which has been turned with a lathe and whichreceives the control assembly that consists of the covers 30 and 32 andthe member 34. Four rollers 44, 45, 46 and 47 are rotatably mounted inthe annular wall 43 of the pressure-applying head 38. The rollers 44 and45 are disposed opposite to each other in a plane. The rollers 46 and 47are disposed opposite to each other in a somewhat more elevated plane.This will be apparent from FIG. 4, in which the member 34 and the lowerand upper cam tracks as well as the covers 30 and 32 are shown indeveloped views. During an operation of the motor 41 thepressure-applying head 38 will rotate in unison with the rollers 44 to47, which ride on the tracks 31 to 33. As soon as the rollers 44 and 45reach the raised portions 48 and the upper rollers 46 and 47 reach therecesses 49 the punch 29 will be forced down against the die 50 to anextent which depends on the height of the raised portions by a movementwhich is transmitted by the guide member 17, the connecting member 19,the hard rubber plate 24, the carrier 23, the pin 25 and thepressure-applying plate 28. As a result, the film lying between thepunch 29 and the die 50 will be punched by parts striking hard againsteach other.

An exact adjustment is effected in that the connecting member 19 isscrewed into the guide member 17 to a larger or smaller depth and isfixed in its adjusted position by the clamp ring 51. It is apparent fromFIGS. 1 and 2 that the punch 29 is mounted by the pins 25 in the upperarm 26 of the toolholder 27 and the die 50 is mounted in the lower arm53 of the toolholder 27. As the toolholder 27 is laterally movable outof the press in the direction of the arrow A, another toolholdercarrying another set of tools can be inserted in a simple manner. Thepress shown in FIG. 3 has the same design as the press which haspreviously been described with reference to FIG. 2 so that a moredetailed description of the present illustrative embodiment is notrequired. It is merely pointed out that the cam tracks 31' and 33',which correspond to the internal cam tracks 31 and 33, are shown aftertheir rotation to a position in which the punching apparatus is in itsclosed position whereas the punching apparatus is shown in its openposition in FIG. 2.

The right-hand side of FIG. 1 corresponds to the left-hand side so thatfurther explanations are not required.

Upon a comparison of FIGS. 2 and 3 it is apparent that the base part 2and the top part 1 are supported on the frames 3 and 4 and the base part2' and the top part 1' in FIG. 3 are supported by the frames 4 and 6.That separate support is necessary because a so-called "hard-on-hard"press must be operated with a very exact adjustment and the two pressesmust not disturb each other, as would be the case, e.g., if the twopresses were mounted on a common frame so that any resilient deflectionsadjacent to one press would inevitably result in a slight change of theposition of the other press.

We claim:
 1. An apparatus particularly suited for intermittentlypunching moving webs made of synthetic thermoplastics, which apparatuscomprises top and bottom tools, which are mounted in a machine frame andat least one of which is connected to a drive for moving said one toolup and down, wherein two punching apparatuses are provided in themachine frame, each of the punching apparatuses includes one of the toptools and one of the bottom tools, respectively, the top tool and thebottom tool of each of said punching apparatuses are secured to arespective pair of parallel frame plates, which are separate from eachother and which have upper and lower ends, said frame plates of eachpair of frame plates are interconnected adjacent their upper ends byupper bars, with the upper bars for each pair of frame plates beingseparate from the upper bars for the other pair of frame plates, and allof said frame plates are fixedly interconnected adjacent their lowerends, thereby supporting said punching apparatuses from separate frameplates.
 2. A punching apparatus according to claim 1, wherein each pairof frame plates constitutes an outer frame plate and an opposite innerframe plate, which constitute carrying plates for associated ones of thetop and bottom tools, with the outer frame plate of each pair of frameplates being in juxtaposed relationship to the inner frame plate of theother pair of frame plates.
 3. A punching apparatus according to claim1, wherein the frame plates of each pair of frame plates are providedadjacent their upper and lower ends with wider portions, which areconsecutively arranged in a longitudinal direction, and the top andbottom tools are fixed to said wider portions.
 4. A punching apparatusaccording to claim 3, wherein the top tools comprise laterallyprotruding arms which bear from below on sliding surfaces of the widerportions of the frame plates.
 5. A punching apparatus according to claim3, wherein the bottom tools bear from above on rails which areconstituted by the wider portions.
 6. A punching apparatus according toclaim 1, wherein each pair of frame plates comprises parts of asub-frame which further comprises the upper bars, the bars being in theform of two parallel side bars, and the sub-frame further compriseslower side bars, the side bars being for holding and guiding respectiveones of the top and bottom tools.
 7. A punching apparatus according toclaim 6, wherein the top and bottom tools are mounted on carriages,which are slidable on and adapted to be fixed to respective ones of thesub-frames.
 8. A punching apparatus according to claim 1, wherein thetop tool is carried by a guide member that is axially slidably andnon-rotatably guided in a slide bushing of a holder and is provided witha peripheral groove, which has side faces that constitute tracks forslide rollers, which are secured to axles of a pressure-applying head,which is mounted in the frame to be rotatable about the axis of theguide member and is axially fixed and which is connected to drive meansfor imparting rotation to said head, and the tracks are so shaped thatthe pressure-applying head by its rotation will impart the desired upand down motion to the guide member.
 9. A punching apparatus accordingto claim 8, wherein the pressure-applying head is rotatably mounted on apin, which is secured to the frame and said pin has a central bore, inwhich a pinlike top extension of the guide member is axially slidablyguided.
 10. A punching apparatus according to claim 8, wherein axles ofthe pressure-applying head are disposed at an angle of 90 degrees witheach other, cam follower rollers are coaxially mounted on mutuallyopposite axles, two of said cam follower rollers ride only on the lowertrack and two only on the upper track of the track groove, the lowerside face is provided with mutually opposite raised portions, the upperside face is provided with mutually opposite, complementary recesses,the said raised portions and recesses are spaced 90 degrees apart.
 11. Apunching apparatus, preferably for punching intermittently moving websmade of synthetic thermoplastics, which apparatus comprises top andbottom tools, which are mounted in a machine frame and at least one ofwhich is connected to a drive for moving said one tool up and down,wherein two punching apparatuses are provided in the machine frame, eachof the punching apparatuses includes one of the top tools and one of thebottom tools, respectively, the top and bottom tool of each of saidpunching apparatuses are secured to sub-frames each comprising twoparallel frame plates, which are separate from each other, said frameplates of each of said sub-frames are respectively interconnectedadjacent their upper ends by upper bars, with the upper bars of eachsub-frame being separate from the upper bars of the other sub-frame, andall of said frame plates are fixedly interconnected at their lower ends,thereby supporting said punching apparatuses on separate sub-frames. 12.An apparatus for punching a workpiece comprising a supporting frame, apair of punching apparatuses, means for mounting said punchingapparatuses on said frame, each punching apparatus comprising an uppertool and a lower tool oriented in opposed relation for contact with theworkpiece, means driving said upper tools to move an upper tool towardand away from a respective one of said lower tools, said frame includinga plurality of pairs of independent frame plates having top portions andbottom portions, top bars connecting the top portions of one pair ofsaid frame plates, separate top bars connecting the top portions of asecond pair of said frame plates, and bottom bars connecting the bottomportions of all of said frame plates, thereby supporting said punchingapparatuses from separate frame plates.
 13. The apparatus as defined inclaim 12 wherein each punching apparatus includes a tool holder havingan upper arm and a lower arm, said lower tool including a die supportedby said lower arm and said frame, said upper tool including a punch,said upper arm including means retaining said punch in alignment withsaid die during movement of the punch toward and away from the die, saidmeans driving said upper tools including a holder supported from saidframe, a guide member movably mounted on said holder and connected withthe punch, a rotatable pressure head mounted on said frame, drive meansrotating said pressure head and a cam track and roller type camfollowers interconnecting said pressure head and guide member to causereciprocation of the guide member and punch connected thereto inresponse to rotation of the pressure head.